Conventionally, various processes for producing quinoline-3-carboxylic acid compounds have bee proposed. These processes include, for example i) a process comprising condensing 2-aminophenyl ketones with keto esters in the presence of a sulfuric acid catalyst in an acetic acid solvent to produce quinoline-3-carboxylic acid compounds, ii) a process comprising dehydrating and condensing 2-aminophenyl ketones with keto esters in the presence of an acid catalyst in a hydrocarbon solvent to produce quinoline-3-carboxylic acid compounds, and the like. The process i) has problems that yields are low as the keto esters are unstable to acids and that the process needs a large amount of acetic acid. Although the process ii) forms a skeleton of quinoline by carrying out dehydration and condensation in a hydrocarbon solvent such as toluene or the like, the process requires a rapid progress of the reaction as keto esters are unstable similarly to the process i), and therefore the process requires a dehydration and reflux under a reduced pressure or use of an excess of keto esters. In addition, the 2-aminophenyl ketones and resulting quinolines have an alkalinity, thereby they make a salt together with an acid as a catalyst to deposit crystal or oil in the reaction solution. Thus, the process has problems that it is delayed or stopped.
Therefore, an object of the present invention is to provide to a process for producing quinoline-3-carboxylic acid compound that is an intermediate useful for pharmaceuticals, briefly in an industrial scale, and in a high yield and purity.